Can the Shingles Vaccine Lower Your Dementia Risk? What the Research Says
Brain Matters · Defy Dementia, Episode 35
Large studies from three countries link the shingles vaccine to fewer dementia diagnoses. Here is what the science shows, what it cannot tell us yet, and one advocate's story of learning about shingles the hard way.
The short answer
Possibly, but it is not proven. Large natural experiments in Wales, Australia and Ontario found that people who became eligible for a free shingles vaccine were diagnosed with dementia less often over the following five to seven years. No randomized trial has tested this yet. The vaccine's proven benefit is protection against shingles.
- In the strongest study, from Wales, getting the vaccine was estimated to reduce new dementia diagnoses over seven years by about one fifth.
- Several studies found a stronger link in women, which may be a clue to how the vaccine works.
- Canada's national advisory committee recommends the shingles vaccine from age 50. Coverage varies by province, so ask your health-care provider.
Could a routine vaccine help protect your brain? In Episode 35 of Defy Dementia, Baycrest's podcast for anyone with a brain, hosts Jay Ingram and Dr. Allison Sekuler look at a growing body of research linking the shingles vaccine to a lower risk of dementia. They hear from Ron Swan, who chairs CARP Nova Scotia and learned about shingles the hard way, and from Dr. Dawn Bowdish, a McMaster University professor who studies the aging immune system. Baycrest cares about this question because finding simple, practical ways to lower dementia risk is at the heart of its work in aging and brain health.
What is shingles?
Shingles is a painful rash caused by the same virus that causes chickenpox. After a childhood bout of chickenpox, the virus stays in the body for life and can wake up years later as shingles. Besides the rash, shingles can cause nerve pain that lasts for months or even years.
Ron Swan knows this first-hand. After spending four or five years advocating with CARP Nova Scotia for a publicly funded shingles vaccine, he got shingles himself, on his right hand and arm, before he had been vaccinated. The rash cleared in about a month, but the nerve pain did not. Dr. Allison Sekuler shared on the episode that she has had shingles twice.
The shingles vaccine used in Canada today is a recombinant vaccine given as two injections, two to six months apart. It uses a protein from the virus to train the immune system and cannot give you shingles. Canada's National Advisory Committee on Immunization recommends it for adults 50 and older, but public coverage varies. Ontario covers it for people aged 65 to 70, with the series completed before the 71st birthday. Nova Scotia began offering it free to people 65 and older in May 2025.
Can the shingles vaccine reduce your risk of dementia?
Possibly. The evidence is promising but not yet proof. Early studies, starting around 2021, found that people who chose to get the shingles vaccine were less likely to be diagnosed with dementia later. The trouble with that kind of study is that people who get vaccinated may differ in many ways from people who do not, for example in overall health, income or how often they see a doctor.
Newer studies get around this problem with what scientists call natural experiments. In Wales, eligibility for a free shingles vaccine was set by exact date of birth: people born on or after September 2, 1933 could get it, and people born even a week earlier could not. Vaccination jumped from almost no one to nearly half of people across that one-week line. Because people born a week apart should be alike in every other way, comparing them is close to a randomized trial. Over seven years, getting the vaccine was estimated to reduce new dementia diagnoses by about one fifth, and the effect was stronger in women.
Similar natural experiments in Australia and in Ontario, which used date-of-birth rules for their own free vaccine programs, found the same pattern. In Australia, eligibility lowered the chance of a new dementia diagnosis over about seven years by 1.8 percentage points.
Dr. Bowdish put the range of estimates across studies at about 17% to 38% lower risk, and said better data are needed to pin the number down. Even so, she called it a really big reduction.
What the evidence can and cannot tell us
Natural experiments are the strongest evidence we have so far, and their results agree across three countries. But they are not randomized trials, which remain the gold standard, and no trial has yet tested the shingles vaccine for dementia. The studies count dementia diagnoses in health records, which can miss or delay some cases. Most of this research looked at an older live vaccine that is no longer used in Canada. And scientists do not yet know how a shingles vaccine would protect the brain. The vaccine's proven benefit is lowering the risk of shingles and its complications.
Does it matter which shingles vaccine you get?
The vaccine studied in Wales, Australia and Ontario was an older live vaccine that has since been replaced in Canada by the two-dose recombinant vaccine. A large US study of more than 200,000 people took advantage of the rapid switch between the two vaccines. People who got the newer vaccine were diagnosed with dementia later than people who got the older one, living about 17% more time without a dementia diagnosis over six years. The newer vaccine was also linked to lower dementia risk than the flu vaccine or the tetanus, diphtheria and pertussis vaccine. Because this study was observational, it shows a link rather than cause and effect, but it suggests the vaccine Canadians receive today is at least as promising.
Why might a shingles vaccine protect the brain?
Nobody knows yet, but Dr. Bowdish described three leading theories. The first is inflammation: when the shingles virus wakes up, it causes a lot of inflammation, and inflammation is linked to dementia. Preventing those flare-ups may prevent the inflammation. The second involves the cold sore virus, a close cousin of the shingles virus that many people carry. It can hide in nerve cells connected to the brain and has long been suspected of playing a role in dementia. The shingles vaccine may offer some cross-protection against it.
The third theory, which Dr. Bowdish finds slightly less compelling but cannot rule out, is that any vaccine gives the immune system a general boost. She said her favourite theory wavers between the first two. Nothing is definitive.
Why might women benefit more than men?
Several studies found a stronger link in women, and scientists are not sure why. Dr. Bowdish said that of four very large studies from different parts of the world, one found protection only in women, two found much greater protection in women, and one found it was equal. That is puzzling, because men and women get shingles at similar rates and respond to the vaccine in similar ways. Dr. Bowdish has a research grant to study this question.
She suspects the answer lies in differences between how men and women handle inflammation. Another idea, which she stressed is only a hypothesis, is that women are more prone to autoimmune reactions after infections. Dr. Sekuler noted that the difference between men and women could itself be a clue to how the vaccine protects the brain.
If you have had shingles, are you already protected?
No. Jay Ingram asked whether having shingles might work like the vaccine. Dr. Bowdish explained that the data suggest the opposite: people who report having had shingles have a higher risk of dementia, and people who have had it more than once have a slightly higher risk still. Getting shingles suggests a gap in your immune protection, which is why people who have had shingles are a higher priority for vaccination. The vaccine helps fill that gap. Ron Swan was told to wait a year after his shingles before being vaccinated, which matches Nova Scotia's guidance that waiting a year after an episode is typically recommended.
Can people living with dementia benefit?
Early evidence suggests they might. A follow-up analysis of the Wales data found that the vaccine was also linked to fewer diagnoses of mild cognitive impairment and, among people already living with dementia, fewer deaths from dementia. These are new findings from a single research group and need to be confirmed.
How does the shingles vaccine compare with exercise, sleep and diet?
It may be one of the easier steps. Dr. Bowdish pointed out that many proven brain-healthy habits are hard to keep up. Getting good sleep can feel like a full-time job, and eating well is out of reach for many people, including for reasons of cost. A vaccine takes two short appointments. It does not replace other healthy habits, and its effect on dementia is not yet proven.
Do other vaccines lower dementia risk?
There are hints that they may. Dr. Bowdish said that for decades, studies have linked vaccines in general, including those for the flu, pneumonia, and tetanus and diphtheria, to lower dementia risk, though the shingles vaccine has shown the strongest link. One possible explanation is that vaccines prevent illness, and illness in older age can bring high levels of inflammation that take a long time to settle. As she put it, "infections are not good for us."
When is the best time to get the shingles vaccine?
For preventing shingles, Canada's national advisory committee recommends it from age 50. For dementia, no one knows yet. Most dementia is diagnosed in people's 80s, but the changes behind it build up over decades. Dr. Bowdish said the question of timing matters for public policy, since some provinces only cover the vaccine within a narrow age window. In Ontario, free vaccination ends at 70, and she said that if a dementia benefit is confirmed, it would make sense to extend coverage to older adults.
In the meantime, Jay Ingram summed up the hosts' view: the decision is fairly easy because the vaccine is already well proven to make shingles much less likely, and a possible lower dementia risk would be an added benefit. The episode's key action is simple: talk to your health-care provider about whether the shingles vaccine is right for you, and check what your province covers.
Frequently asked questions about the shingles vaccine and dementia
Does the shingles vaccine prevent dementia?
It has not been proven. Several large natural experiments found fewer new dementia diagnoses among people who became eligible for the shingles vaccine, which is promising. But no randomized trial has tested the vaccine for dementia yet, and scientists do not know how it might work. Its proven benefit is protection against shingles.
How much could the shingles vaccine lower dementia risk?
Estimates vary. In a study from Wales, getting the vaccine was estimated to reduce new dementia diagnoses over seven years by about one fifth. Dr. Dawn Bowdish of McMaster University said studies range from about a 17% to a 38% lower risk, and better data are needed to pin the number down.
Is the shingles vaccine used in Canada the same one that was studied?
Not exactly. The studies from Wales, Australia and Ontario looked at an older live vaccine that is no longer used in Canada. Today Canadians receive a two-dose recombinant vaccine. A large US study found it was linked to lower dementia risk than the older vaccine, but that study was observational.
Who should get the shingles vaccine in Canada?
Canada's National Advisory Committee on Immunization recommends the shingles vaccine for adults 50 and older who have no reason to avoid it. Whether it is free depends on your province and age. For example, Ontario covers it from 65 to 70, and Nova Scotia covers it from 65. Ask your health-care provider.
I have had shingles. Should I still get the vaccine?
Having shingles does not mean you are protected. Dr. Bowdish explained that people who have had shingles are more likely to get it again, so they are a higher priority for vaccination. Nova Scotia guidance says waiting about a year after an episode is typically recommended. Your health-care provider can advise on timing.
Why might the shingles vaccine affect dementia risk?
No one knows yet. Leading ideas include preventing the inflammation caused when the shingles virus wakes up, offering some protection against the related cold sore virus, and a general boost to the immune system that any vaccine may give. Dr. Bowdish said none of these theories is definitive.
Research referenced
- Scherrer JF, Salas J, Wiemken TL, Hoft DF, Jacobs C, Morley JE. Impact of herpes zoster vaccination on incident dementia: a retrospective study in two patient cohorts. PLoS ONE. 2021;16(11):e0257405. doi:10.1371/journal.pone.0257405
- Taquet M, Dercon Q, Todd JA, Harrison PJ. The recombinant shingles vaccine is associated with lower risk of dementia. Nature Medicine. 2024;30:2777-2781. doi:10.1038/s41591-024-03201-5
- Eyting M, Xie M, Michalik F, Heß S, Chung S, Geldsetzer P. A natural experiment on the effect of herpes zoster vaccination on dementia. Nature. 2025;641(8062):438-446. doi:10.1038/s41586-025-08800-x
- Pomirchy M, Bommer C, Pradella F, Michalik F, Peters R, Geldsetzer P. Herpes zoster vaccination and dementia occurrence. JAMA. 2025;333(23):2083-2092. doi:10.1001/jama.2025.5013
- Xie M, Eyting M, Bommer C, Ahmed H, Geldsetzer P. The effect of shingles vaccination at different stages of the dementia disease course. Cell. 2025;188(25):7049-7064.e20. doi:10.1016/j.cell.2025.11.007
- Pomirchy M, Chung S, Bommer C, Strobel S, Geldsetzer P. Herpes zoster vaccination and incident dementia in Canada: an analysis of natural experiments. The Lancet Neurology. 2026;25(2):170-180. doi:10.1016/S1474-4422(25)00455-7
Further reading
- Bowdish D. Is dementia a vaccine-preventable condition? Video talk, Bowdish Lab, McMaster University. bowdish.ca
- Can a routine vaccine prevent dementia? Harvard Health Publishing, Harvard Medical School. health.harvard.edu
Hear the full episode
Hear Ron Swan's shingles story and Dr. Dawn Bowdish's clear explanation of what the research on the shingles vaccine and dementia does and does not show.
Listen to Episode 35 Support brain health research at BaycrestMeet the hosts of Defy Dementia
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